BIOL 2500 Lecture 13: BIOL 2500 – Lecture 13

• School: University of Manitoba
• Department: Biological Sciences
• Course: BIOL 2500
• Professor: Roman Gietz

Document Summary

Natural selection favouring heterozygotes: called heterozygote advantage or overdominance, natural selection that favours heterozygotes eventually leads to a dynamic equilibrium called balanced polymorphism, genetic diversity is maintained. Selection favours heterozygotes at the expense of each type of homozygote. Symbolically, natural selection favouring heterozygotes can be represented in this way: waa < waa > waa. If opposing selective forces are balanced, allele frequencies are no longer changing. Sickle cell anemia in humans is associated with a balanced polymorphism. If genotypes are as follows: baba - normal but susceptible to malaria. Fitness = 0. 75: babs - normal with some protection against malaria. Fitness = 1: bsbs - sickle cell anemia. If the system is a balanced polymorphism, calculate the frequency of the two alleles at the point of equilibrium. Steps: calculating the selection coefficients using realtive fitness, draw table, using the selection coefficients, calculate pe and qe, write formulas.